728.2 DISSEMINATION AND EXHIBITION OF OBSCENE MATERIAL TO MINORS. Any person, other than the parent or guardian of the minor, who knowingly disseminates or exhibits obscene material to a minor, including the exhibition of obscene material so that it can be observed by a minor on or off the premises where it is displayed, is guilty of a public offense and shall upon conviction be guilty of a serious misdemeanor.

728.7 EXEMPTIONS FOR PUBLIC LIBRARIES AND EDUCATIONAL INSTITUTIONS. Nothing in this chapter prohibits the use of appropriate material for educational purposes in any accredited school, or any public library, or in any educational program in which the minor is participating. Nothing in this chapter prohibits the attendance of minors at an exhibition or display of art works or the use of any materials in any public library.

If a library does filter, they must be able to turn it off for an adult that requests it.